Both Sunday Without God and Venus Versus Virus have anime and manga, and since your comment doesn't specify which fandom, I'll answer for both.
Sunday Without God's manga only covers the Valley of Death arc, whereas the anime covers that arc in three episodes, so it goes further than the manga. (It's based on a series of light novels, but the novels aren't available in English, so don't worry about those.)
For Venus Versus Virus, the anime and manga have the same plot, but different endings (for one, there are more character deaths in the anime), and the main antagonist is a little different, and the manga also goes into more detail about Lucia's and Sumire's powers. I'm familiar with both, and I've never seen anyone else request the canon, so I've never felt the need to separate them.
no subject
Sunday Without God's manga only covers the Valley of Death arc, whereas the anime covers that arc in three episodes, so it goes further than the manga. (It's based on a series of light novels, but the novels aren't available in English, so don't worry about those.)
For Venus Versus Virus, the anime and manga have the same plot, but different endings (for one, there are more character deaths in the anime), and the main antagonist is a little different, and the manga also goes into more detail about Lucia's and Sumire's powers. I'm familiar with both, and I've never seen anyone else request the canon, so I've never felt the need to separate them.